1. Field of the Invention
The present invention relates to a keyboard device which is applied to an electronic keyboard instrument, such as an electronic piano, and a mounting structure of a let-off imparting member for imparting a let-off feeling closely analogous to a let-off feeling provided by an acoustic piano.
2. Description of the Related Art
Conventionally, as a keyboard device for an electronic piano, there has been known one disclosed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 2010-262129 filed by the present assignee. The keyboard device includes a plurality of swingable keys, a plurality of hammers provided in association with the respective keys and each configured to pivotally move in accordance with depression of an associated key, and a key switch for detecting key depression information on the keys. Each of the keys is swingably supported by a balance pin erected through a balance pin hole formed in a central portion of the key in the front-rear direction. Each of the hammers is pivotally supported by a metal action chassis formed into a predetermined shape by extrusion processing, via a bearing in the rear end of the hammer, and is placed on the rear end of the upper surface of the associated key via a capstan screw screwed into the hammer from below at a predetermined location forward of the bearing. The key switch is comprised of a switch board formed by a printed circuit board and a plurality of switch bodies provided on the hammer side of the printed circuit board in association with the respective hammers. The key switch is mounted to the lower side of a switch mounting part formed in the upper portion of the action chassis. More specifically, the rear end of the switch board is engaged with the base portion of the switch mounting part, and the front end of the switch board is secured to the switch mounting part with screws via a spacer.
Further, in the keyboard device, the ratio between a length from the front end of a key to an associated balance pin (hereinafter referred to as “the key front portion length”) and a length from the balance pin to a capstan screw via which an associated hammer is in abutment with the key (hereinafter referred to as “the key rear portion length”) is set to approximately 3:2.
Further, the keyboard device for an electronic keyboard instrument, disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2010-262129, is equipped with a let-off function for imparting a let-off feeling. In the keyboard device, each hammer that pivotally moves in accordance with depression of an associated key is pivotally supported by the action chassis formed by the metal extrusion molded article, as will be described hereinbelow. The keyboard device has let-off members provided in association with the respective hammers, and when a key is depressed, an engaging projection of an associated hammer comes into temporary engagement with an associated one of the let-off members during a pivotal motion of the hammer, whereby a let-off feeling is imparted to the touch feeling of the depressed key.
Each let-off member includes a mounting part and a body part extending forward and downward from the mounting part. The thus constructed let-off member has the mounting part mounted to a holder and the body part mounted to the upper portion of the action chassis via the holder in facing relation to an associated hammer. More specifically, the let-off members associated with the respective hammers are mounted to the holder extending in the left-right direction, and the holder is fixedly secured to the action chassis with screws, whereby the let-off members are mounted to the action chassis, in a state arranged side by side in the left-right direction.
The above-described keyboard device is configured such that the key switch is mounted to the lower side of the switch mounting part of the action chassis, which makes key switch mounting work troublesome. In addition, e.g. when adjustment is necessitated after mounting of the key switch to the action chassis during manufacturing of the electronic piano, or when maintenance of the electronic piano is necessitated, as well, work for dismounting the key switch from the action chassis and subsequent work for mounting the key switch again are troublesome.
Further, since the switch board of the key switch is secured to the action chassis with screws via the spacer, there is a fear that the switch board of the key switch or the switch bodies cannot be appropriately positioned with respect to the hammers with high accuracy e.g. due to a dimensional error in manufacturing of the spacer.
Furthermore, generally, an electronic piano is demanded to be made compact in the depth dimension, and hence the length of an entire key in the front-rear direction is set to be shorter than that in an acoustic grand piano (hereinafter simply referred to as “the grand piano”). Further, in the conventional keyboard apparatus, the ratio between the key front portion length and the key rear portion length is set to approximately 3:2 as mentioned above, and therefore the key front portion length of the keyboard apparatus is far shorter than that of the grand piano. For this reason, when an electronic piano provided with the above-described keyboard device is played on, the difference in load e.g. between depression of a portion of a key close to the front end thereof and depression of a portion of the key rearwardly remote from the front end is larger than when a grand piano is played on, which makes it impossible to obtain touch feeling sufficiently similar to that provided by the grand piano. Thus, the above-described keyboard device leaves room for improvement.
Further, in the above-described keyboard device, the engaging projection of each hammer is engaged with and disengaged from the distal end of an associated let-off member, whereby a let-off feeling is imparted. For this reason, it is demanded that the relationship between the hammer and the let-off member, the attitude of the entire let-off member, and the position of the distal end of the same have high accuracy. However, in the conventional keyboard device, since the let-off members are mounted to the action chassis via the holder secured to the action chassis with screws as described hereinabove, the let-off members sometimes cannot be accurately positioned with respect to the respective hammers directly mounted to the action chassis. In addition, when variation occurs in the attitude or the position of the distal end between the let-off members, there is a fear that a let-off feeling cannot be uniformly and stably imparted to all the keys during key depression. Therefore, the above-described keyboard device leaves room for improvement in respect of the mounting structure of a let-off member as well.